Originally Posted by Martycool007
Question for: FOH
Is that 3" thick "Safe-n-Sound" being used for absorbing panels for the mid to high frequencies? How does it compare to 4" OC703 for that purpose, and, would it be best to also go with a 4" air gap for this purpose similar to the OC703 panels?
It's being used as a broadband absorber, and spacing it off the surface makes it even more broadband.
I like SafenSound Rockwool because it's cost effectiveness. We can split hairs and go into the minutia, but what's important is it's acoustically very similar to OC703, it's just slightly less handy to deal with,.. doesn't entirely hold it's shape like 703, but no problem.
Yes, the gap is important. Myself, I'd recommend double thickness of the 3" SafenSound, spaced off the boundary. That yields a more broadband absorber, which is the point. You do not merely want to filter the reflected energy.
Originally Posted by Martycool007
Would it work even better if I were to go with two layers that would total 6" thick with a 4" to 6" air gap?
For my bass traps, I plan to use R-19 pink fluffy stuff in each corner cut into triangles and stacked from floor to ceiling, or would Safe-n-Sound work better?
For the new ceiling panels that I am going to construct, would it be ok to use the 16" wide & 3" deep Safe-n-Sound made into 32" wide by 5' long and 6" deep with a 4" or possibly 6" air gap? Or should I just save up and spring for the OC703?
Yeah, the thicker the better, and a 4" gap or 6" gap is fantastic.
For ceiling clouds, I like the more rigid 703, just for user friendliness. But, the rockwool safensound is fine.
It's often recommended that employing 4" thick OC703, or 4" Rockwool, 4" air-gap is adequate for attenuation of specular reflections. Each room is somewhat different wrt the transition region, and loudspeakers typically lose directivity in the lower octaves, so if you need to address these reflections, the treatment needs to be thick enough to work.
As I mentioned above, by using treatment panels to absorb this reflected energy, it is important that they're effective (either via thickness, spacing, or both), so they don't simply attenuates the MF and HF. Thus making a more dull and lifeless reverberant field. Don't EQ the reflection, if it's a problem, either redirect it, diffuse/scatter it, or absorb it.
Bass trapping; Marty, either fluffy or SafenSound, it's all about GFR, gas flow resistivity, ... and this can be independent of density.
For the corner porous bass trapping, they need to be as thick as possible... as thick/big as you can sacrifice. Remember, with the thicker corner traps, a material with lower gas flow resistivity is what you want. Pink fluffy, or any fluffy, insulation that loose and uncompressed will be your best bet. It's both the cheapest and most effective.
Yes, any material stacked in there to the same dimensions will work, there are many examples of rigid 703 thickly stacked to the ceiling, ... and they'll work fine. It's just not the most optimal use of material. If I had that much rigid, I'd span each diagonal in the room, all 12 junctions. This is because covering more surface area works quite well. 4" rigid, spanning the corner, with a big air gap behind, is proven quite effective too. Surface area rules (if I had a finite amount of OC703 rigid, for trapping, I wouldn't stack it all up in the corner. I'd span as many corners as possible .. each four main vertical corners, the four ceiling/wall corners, etc.).
It just all depends what material you use, how much space you are will to give up to the treatment thickness.
If you want to use 4", use rigid 703 or equivalent product. If you want to use something from 6"-12", I'd say the Safe-N-Sound Rockwool, anything thicker fluffy is likely your best use of material and space. The fluffy does require being mindful of not over-compressing, and you can use some plastic bird netting, or similar .. to help it not to compress too much.
But again, you can use 8" thick of rigid if you want. Some use rigid, Superchunk style, stacking triangles of rigid in the corners .. floor to ceiling. As I said above, it works, it's just expensive.
Also, the more dense the material is, it looses it's ideal effectiveness. That's why it's so nice to see fluffy is both the cheapest and most effective at the super treatments. It's just a pain to deal with. It's been suggested a 34" face (corner) or larger, and fluffy is the way to go.
Now, if you find you're loosing too much MF/HF, and your room becomes a bit over-damped and lifeless, you can face any of your treatment panels and bring back that precious energy. Most simply use like a 6mil plastic ... common Visqueen. You could employ paper facing, and it will start to reflect somewhere around 1khz. A "pool liner" thickness of vinyl will return around 500hz and up. If needed, you can use 1/2lb mass loaded vinyl, it exhibits returns around 250hz and up.
To assure not to over dampen, ideally the ETC is the tool to determine placement. Some don't mind the over-damped environment.
Now the bad news, velocity based porous absorbers are actually the wrong tool for the job ... in small room and close to the boundaries. Velocity based absorption needs to be as close to the 1/4 wave point as possible, here's an image from Ethan Winer's whitepaper;
Unless you really can give up huge amounts of space, there are better methods, ie., pressure based absorption. Helmholtz resonators, tuned traps, pressure based absorption is really beyond the scope of this post. Suffice it to say, porous corner traps, as effective as they are, are relatively
ineffective. I'd be glad to discuss pressure based approaches (if anyone's interested), but velocity based porous absorption is so much better suited for the DIY community.
Check this out just for comparison sake;
2" on wall
Hope this helps